SFPD patrol car
Photo by Eleni Balakrishnan

Two current San Francisco police officers and one part-time retired San Francisco police officer were taken into custody today by their employer for charges including theft of a machine gun from the SFPD and destruction of evidence.

The SFPD announced the arrests today, noting that warrants for the three officers, involved in two unrelated cases of misconduct, were issued on Friday, April 15, and that all three officers surrendered themselves for arrest today. The incidents occurred in the summer of 2021.

Shortly after the SFPD’s announcement, the District Attorney’s office released a statement detailing the allegations against the three officers and announcing the DA’s charges.

Tenderloin Station Officers Kevin Lyons and Kevin Sien, who were found in an internal investigation to have destroyed evidence in a July, 2021, case, have already been released from jail and appear to be still employed with the department, in non-public-facing roles.

According to a statement from the District Attorney’s office, employees at the San Francisco Marriott Marquis hotel last year called the police for suspected criminal activity after discovering several credit cards, IDs, and drugs in a delinquent guest’s luggage.

MP5SD machine gun, of the sort that retired Officer Mark Williams allegedly stole from the department. Photo from Heckler-Koch website

Instead of collecting and cataloguing the evidence, which Lyons and Sien purportedly said would be too time-consuming, the officers allegedly shredded the credit cards and IDs. Lyons allegedly flushed the drugs down a toilet. DA spokesperson Rachel Marshall today called the incident “quite disturbing.”

​​“San Francisco residents trust the police to conduct the investigative work, so my office can bring cases that keep the city safe,” said District Attorney Chesa Boudin in a statement today. “These officers undermined their own colleagues, my office, and our criminal justice system as a whole, by destroying and concealing the evidence of a crime, simply because they didn’t want to take the time to do their jobs.”

Lyons and Sien were determined, by an internal investigation, to be responsible for destruction of evidence, and the two officers — a 21-year veteran and 5-year veteran of the SFPD, respectively — were removed “immediately” from their public-facing positions, according to the department.

Neither the SFPD nor the DA’s office has confirmed when its investigations concluded or when they identified the two officers who destroyed evidence. It is unclear why it took the better part of a year to issue their arrest warrants.

In the second case, the SFPD discovered a missing Heckler & Koch MP5 SD submachine gun during a routine inventory check in August, 2021. According to the DA’s office, the SFPD was preparing 22 of these guns for destruction. The Internal Affairs Division, which investigates cases of misconduct within the department, began an investigation. Within four days, retired Officer Mark Williams, who worked part-time for the SFPD, purportedly confessed to having taken the weapon to his home in Napa.

He was “immediately” terminated from his position, according to the SFPD. Some eight months later, a warrant was issued on April 15 for Williams’ arrest, and today he turned himself in.

Williams is not currently in the county jail booking log, but may still be in custody. According to the SFPD, he faces charges for unlawful possession of a machine gun, possession of a silencer, and embezzlement.

Lyons and Sien were cited for destroying or concealing evidence, and were both released from custody the same day.

“The actions of these SFPD members violate the law, and regrettably fall far short of our department’s shared values,” said San Francisco Police Chief Bill Scott. “As sworn police officers, we have no higher obligation than to earn and maintain public trust, and we are disappointed that these incidents detract from the outstanding work done by our officers and non-sworn members every day.”

Scott said the police department presented the cases to the District Attorney’s Office for prosecution, and praised the department’s “commitment to accountability and the principle that no one, including a current or retired police officer, is above the law.”

All three officers are set to be arraigned on May 19.


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REPORTER. Eleni is our reporter focused on policing in San Francisco. She first moved to the city on a whim nearly 10 years ago, and the Mission has become her home. Follow her on Twitter @miss_elenius.

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  1. The employer needs to be much more responsible for their wayward (cops) employEES. 2 unrelated incidents?? …more like 200 and employer treating this too lightly!!

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  2. What a surprise? in the midst of trying to restructure investigations (a major point called for by every outside review in the past five or six years) the SFPD actually investigates and charges its own. Dont be fooled. Don’t allow them to take the lead on investigations, particularly OIS.

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  3. Wow, SFGate didn’t mention that it was a silenced weapon. Seems like a pretty big omission

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